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I have two question regrading sound waves.

The first one:

The pressure P(x;t) at a point x at time t in a medium through which a harmonic wave is

travelling can be described by:

P(x,t) = Asin(wt -kx)

If the equation describes a pressure wave travelling in air, with amplitude 2 Pa and frequency 100 Hz,

find the instantaneous pressure at a distance 10 cm from the source at time 5s.

My solution(am I doing right?):

w=2pi*f

w=2pi*100Hz = 200pi rad/sec;

k=2pi/λ; v=f*λ; λ=343m/s /100 Hz = 3.43m and k=2pi/3.43 =1.83 rad/m;

Finally I have this:

P(x=0.1 ,t=5) = 2sin(200pi*5 -1.18*0.1) = -0.34.

The second question is here

Hope you can help me to figure out the solutions.

Thanks